1. Field of the Invention
The present invention generally relates to a transverse element for a drive belt for a continuously variable transmission.
2. Description of the Related Art
The present invention relates to a transverse element for a drive belt for a continuously variable transmission having two pulleys having an at least partially conical contact surface for pairwise enclosing of the drive belt, each pulley being composed of two pulley sheaves, the drive belt comprising two endless carriers and transverse elements which are placed against each other in axial direction of the drive belt, wherein two subsequent transverse elements are tiltable relative to each other about a contact line, and wherein the transverse elements on both sides are provided with a supporting surface for supporting a carrier, which supporting surface transforms into a pulley sheave contact surface being designed to abut against a contact surface of a pulley sheave, through a transition region.
Such a transverse element is generally known, and is designed for application in a drive belt for a continuously variable transmission. Such a drive belt comprises two bundles of endless bands being shaped like a closed loop, which function as carriers of a number of transverse elements. The transverse elements are continuously arranged along the entire length of the bands, in order for them to be able to transmit forces which are related to a movement of the drive belt during operation.
The transverse elements are on both sides provided with recesses for at least partially receiving the bundles of bands. Further, the transverse elements comprise supporting surfaces for supporting the bundles of bands.
Furthermore, for the purpose of contact between the transverse elements and the pulley sheaves of the continuously variable transmission, the transverse elements on both sides are provided with pulley sheave contact surfaces which are divergent in the direction of the supporting surfaces. A supporting surface and a pulley sheave contact surface being situated at one side of a transverse element are connected to each other through a convex transition region. In the case of known transverse elements, the transition region has the same curvature radius along its entire length.
In case of a relatively small value being chosen for the curvature radius of the transition region, for example 0.3 mm, an advantage is that a relatively large pulley sheave contact surface is obtained. Another advantage is that also a relatively large supporting surface results. However, there are also a number of disadvantages associated with the choice of a relatively small curvature radius.
A first disadvantage is connected to the production process of the transverse elements. The transverse elements are formed from basic products being obtained by means of cutting. In practice, it was found that in case of a relatively small curvature radius of the transition region upsets arise in said region during further process steps, probably as a result of mutual contact between the basic products, or as a result of a finishing process, like in particular tumbling. Transverse elements wherein this is the case can cause damages onto the bands, especially in case of the assembly of the drive belt, wherein the carrier is pushed into a recess of the transverse element along the transition region. Damages to the bands increase the chance of for example breaking of the bands.
A second disadvantage is that a transition region having a relatively small curvature radius is more sensitive to damage than a transition region having a larger curvature radius. This effect is being contributed to by (Hertz) contact tensions which in first order are inversely proportionate to the curvature radius and which can occur in the transition region during finishing processes of the basic products of the transverse elements and during assembly of the drive belt. A damage of the transition region can cause a damage of the bands, as already indicated in the above.
It is true that applying a larger curvature radius for the transition region offers a solution to above-mentioned disadvantages, but in that case, a decrease of the pulley sheave contact surface occurs as important disadvantage.
Another disadvantage is that a decrease of the supporting surface occurs, in a similar manner.
It is an object of the present invention to shape the transition region such that the disadvantages of a small curvature radius are totally or at least partially dissolved, without the occurrence of disadvantages of a large curvature radius. According to the present invention, this object is achieved by providing for a transverse element of the type being mentioned in the first paragraph, which is wherein the transition region comprises two parts having different curvature radii, wherein a first curvature radius of a first part near the side of the supporting surface is larger than a second curvature radius of a second part near the side of the pulley sheave contact surface.